.\"	$OpenBSD: tftp-proxy.8,v 1.1 2005/12/28 19:07:07 jcs Exp $
.\"
.\" Copyright (c) 2005 joshua stein <jcs@openbsd.org>
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd November 28, 2005
.Dt TFTP-PROXY 8
.Os
.Sh NAME
.Nm tftp-proxy
.Nd Internet Trivial File Transfer Protocol proxy
.Sh SYNOPSIS
.Nm tftp-proxy
.Op Fl v
.Op Fl w Ar transwait
.Sh DESCRIPTION
.Nm
is a proxy for the Internet Trivial File Transfer Protocol invoked by
the
.Xr inetd 8
internet server.
TFTP connections should be redirected to the proxy using the
.Xr pf 4
.Ar rdr
command, after which the proxy connects to the server on behalf of
the client.
.Pp
The proxy establishes a
.Xr pf 4
.Ar rdr
rule using the
.Ar anchor
facility to rewrite packets between the client and the server.
Once the rule is established,
.Nm
forwards the initial request from the client to the server to begin the
transfer.
After
.Ar transwait
seconds, the
.Xr pf 4
NAT state is assumed to have been established and the
.Ar rdr
rule is deleted and the program exits.
Once the transfer between the client and the server is completed, the
NAT state will naturally expire.
.Pp
Assuming the TFTP command request is from $client to $server, the
proxy connected to the server using the $proxy source address, and
$port is negotiated,
.Nm
adds the following rule to the anchor:
.Bd -literal -offset indent
rdr proto udp from $server to $proxy port $port -\*(Gt $client
.Ed
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl v
Log the connection and request information to
.Xr syslogd 8 .
.It Fl w Ar transwait
Number of seconds to wait for the data transmission to begin before
removing the
.Xr pf 4
.Ar rdr
rule.
The default is 2 seconds.
.El
.Sh CONFIGURATION
To make use of the proxy,
.Xr pf.conf 5
needs the following rules.
The anchors are mandatory.
Adjust the rules as needed for your configuration.
.Pp
In the NAT section:
.Bd -literal -offset indent
nat on $ext_if from $int_if -\*(Gt ($ext_if:0)

no nat on $ext_if to port tftp

rdr-anchor "tftp-proxy/*"
rdr on $int_if proto udp from $lan to any port tftp -\*(Gt \e
    127.0.0.1 port 6969
.Ed
.Pp
In the filter section, an anchor must be added to hold the pass rules:
.Bd -literal -offset indent
anchor "tftp-proxy/*"
.Ed
.Pp
.Xr inetd 8
must be configured to spawn the proxy on the port that packets are
being forwarded to by
.Xr pf 4 .
An example
.Xr inetd.conf 5
entry follows:
.Bd -literal -offset indent
127.0.0.1:6969	dgram	udp	wait	root \e
	/usr/libexec/tftp-proxy	tftp-proxy
.Ed
.Sh SEE ALSO
.Xr tftp 1 ,
.Xr pf 4 ,
.Xr pf.conf 5 ,
.Xr ftp-proxy 8 ,
.Xr inetd 8 ,
.Xr syslogd 8 ,
.Xr tftpd 8
.Sh CAVEATS
.Nm
chroots to
.Pa /var/empty
and changes to user
.Dq proxy
to drop privileges.
